1. Field of the Invention
The present invention relates to a liquid-ejection head for ejecting liquid, and a method for manufacturing a liquid-ejection head substrate used in a liquid-ejection head.
2. Description of the Related Art
An inkjet recording head used in inkjet recording is an exemplary liquid-ejection head for ejecting liquid.
U.S. Pat. No. 6,143,190 discloses a method for forming, by anisotropic etching, an ink supply port that is in communication with and supplies liquid to a liquid chamber having ejection-energy generating portions for generating heat energy for jetting droplets from ejection orifices. U.S. Pat. No. 6,143,190 also discloses a method for precisely forming an ink supply port, using a sacrifice layer. U.S. Pat. No. 6,143,190 discloses the role served by the sacrifice layer during precise etching, for example, in FIGS. 1 to 3 and the description of the first embodiment related to these figures. U.S. Pat. No. 7,250,113 discloses a method for simplifying steps while performing precise etching, by simultaneously performing a step of forming a sacrifice layer and another step.
These ink supply ports are formed by anisotropically etching a silicon (Si) substrate having a <100> plane orientation, using an alkaline solution. This method utilizes the difference in dissolution rate in an alkaline solution among plane orientations. More specifically, etching progresses while leaving a <111> plane, whose dissolution rate is extremely low.
FIG. 7 is a schematic sectional view showing an exemplary ink supply port formed by using a known sacrifice layer and anisotropic etching process. FIG. 7 shows a Si substrate 51, a portion 52 where a sacrifice layer existed, an etching stop layer 54, an etching mask 58, and <111> planes 55 of the Si substrate. As shown in FIG. 7, the <111> planes 55 have a slope of 54.7° with respect to the back surface of the Si substrate 51. Thus, when a through-opening is formed in the Si substrate 51 having a thickness T using a known Si anisotropic etching process, for example, a surface subjected to etching needs to have a width of at least (2 T/tan 54.7°), geometrically. This is an obstacle to a reduction in size of chips or processing in a back-end process, such as a die bonding step, of chips.
U.S. Pat. No. 6,107,209 discloses a method that solves the above-described problem, in which anisotropic etching is performed after heat treatment of a Si substrate. According to the method, an ink supply port having a barrel-shaped cross section is formed, in which the processing width of <111> planes increases to a desired height from the back surface of the Si substrate, and then the processing width of <111> planes decreases.
U.S. Pat. No. 6,805,432 discloses a method for forming an ink supply port having a barrel-shaped cross section, in which anisotropic etching is performed after dry etching.
However, the shapes of ink supply ports (the positions of the bulges of barrel shapes) that can be formed according to the method for forming an ink supply port having a barrel-shaped cross section, disclosed in U.S. Pat. No. 6,107,209, are limited for a processing reason. If there is any defect in the crystal structure of a Si substrate, the state of progress of etching is changed at the defect portion, thereby making it impossible to obtain an ink supply port having a desired shape. Thus, it is difficult to stably form desired ink supply ports regardless of the crystal structure of Si substrates.
Further, a load in the manufacturing process is heavy in the method for forming an ink supply port having a barrel-shaped cross section, disclosed in U.S. Pat. No. 6,805,432. More specifically, a dry etching step for forming a deep groove in a Si substrate takes long time. Moreover, because there are pre- and post-dry etching steps, such as application, exposure, development, and removal steps, time and effort for these steps are required.